(1) Field of the Invention
The present invention relates generally to a tool for applying pressure to an object, and in particular to a hand tool for applying a controlled pressure to nuts and other items.
(2) Description of the Prior Art
Most tools or devices for producing compression on a workpiece do so directly, usually using a form of lever action. When used as a nutcracker, such tools usually comprise a pair of straight-legged lever arms, hinged together at one end and having a mutually opposed roughened jaw sections on the lever arms. A nutcracker of this configuration has a serious disadvantage. While exerting maximum pressure on the nutshell there is a simultaneous effort to stop the crushing action at the instant of cracking the shell to prevent damage to the nutmeat. The requirement to control the pressure to prevent or minimize damage to the nutmeat at this time of exertion of maximum pressure on the nutshell is a task often impossible to achieve.
U.S. Pat. No. 4,614,034 to the present inventor describes a nutcracker in which the inward movement of the lever arms is limited when a nut is being crushed. The tool described in that patent is comprised of a pair of lever arms that are hinged at their ends by pins that are drawn toward each other by a spring. Each lever arm includes in inwardly facing, curved stop arm, having gear engaging teeth on the inner part of the curve.
A gear is positioned on either side of the tool, with one gear being in a plane with each top arm, so that one stop arm is positioned above one gear and the other stop arm is positioned beneath the other gear. A shaft is affixed to one gear and extends through an opening or receptacle in the other gear, with the receptacle being shaped to allow limited rotational movement of the shaft.
When a workpiece is not present, the hinged ends of the lever arms are held together by the spring, holding the stop arms away from the gears. However, when a workpiece is inserted between the lever arms, and the arms are compressed against the workpiece, the hinged ends are levered apart, causing the stop arms to engage the gears. With further compression, the stop arms rotate the gears in opposite direction, until the movement of the shaft within the receptacle reached a predetermined limit.
At that point, rotation of the gears is stopped, preventing further movement of the stop arms. Thus, the movement of the lever arms is also stopped at the predetermined limit. As a result, when cracking the shell of a nut, the lever arms can move toward each other sufficiently to crack the nut shell, but will stop before the nut meat is crushed.
While the above tool is generally effective in providing a controlled compression, there is still a need for a more rugged tool that would perform this function in a simple manner.